OPENCV学习笔记12_扫描图像并访问相邻像素

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
using namespace cv;
void sharpen(const Mat &image, Mat &result) ;
void sharpen2D(const Mat &image, Mat &result);

int main()
{
    Mat image = imread("test.jpg");
    resize(image, image, Size(), 0.6, 0.6);
    Mat result1;
    Mat result2;

    namedWindow("YunFung Image");
    imshow("YunFung Image", image);

    sharpen(image, result1);
    namedWindow("Result1");
    imshow("Result1", result1);

    sharpen2D(image, result2);
    namedWindow("Result2");
    imshow("Result2", result2);

    waitKey();
    return 0;
}

void sharpen(const Mat &image, Mat &result) {
    result.create(image.size(), image.type());   // allocate if necessary
    int nchannels = image.channels();

    for (int j = 1; j < image.rows - 1; j++) {    // for all rows (except first and last)
        const uchar* previous = image.ptr<const uchar>(j - 1);  // previous row
        const uchar* current = image.ptr<const uchar>(j);        // current row
        const uchar* next = image.ptr<const uchar>(j + 1);        // next row

        uchar* output = result.ptr<uchar>(j);                   // output row pointer
        //saturate_cast<uchar>  changing negative values to 0 and values over 255 to 255
        //sharpened_pixel = 5 * current - left - right - up - down;
        for (int i = nchannels; i < (image.cols - 1)*nchannels; i++) {
            *output++ = saturate_cast<uchar>(5 * current[i] - current[i - nchannels]
                                                                - current[i + nchannels] - previous[i] - next[i]);
        }
    }

    // Set the unprocessed pixels to 0   - left - right - up - down
    result.row(0).setTo(Scalar(0));
    result.row(result.rows - 1).setTo(Scalar(0));
    result.col(0).setTo(Scalar(0));
    result.col(result.cols - 1).setTo(Scalar(0));
}
void sharpen2D(const Mat &image, Mat &result) {

    // Construct kernel (all entries initialized to 0)
    Mat kernel(3, 3, CV_32F, Scalar(0));
    // assigns kernel values
    kernel.at<float>(1, 1) =  5.0;
    kernel.at<float>(0, 1) = -1.0;
    kernel.at<float>(2, 1) = -1.0;
    kernel.at<float>(1, 0) = -1.0;
    kernel.at<float>(1, 2) = -1.0;

    //filter the image
    filter2D(image, result, image.depth(), kernel);
}